From the mid-1960s onwards, the late Slovakian artist Július Koller performed small interruptive acts in public and private spaces, creating situations that insinuated how reality might be—and become—otherwise. Such modest acts might consist of, for instance, staging table tennis matches in art spaces, graffitiing question marks or endless waves onto street walls with whipped cream, taking friends on mountain hikes up to a fictional U.F.O. gallery (“galéria” in Slovakian also means “moutain plateau”), or sending people his thoughts in the mail via postcards with diagrammatic texts.